JP6444699B2 - Load tap changer - Google Patents

Description

  Embodiments described herein relate generally to an on-load tap switching device.

  2. Description of the Related Art For example, a vacuum valve cutoff type on-load tap switching device that switches a transformer tap without interrupting a load current is known. This type of on-load tap switching device includes, in addition to a vacuum valve, for example, a lead conductor that functions as a relay terminal for connecting a flat knitted wire.

  The vacuum valve includes a movable shaft having a movable electrode paired with a fixed electrode at one end and the other end protruding outward. On the other hand, the lead conductor is fixed to the other end of the movable shaft so as to face the vacuum valve. Moreover, the vacuum valve and the lead conductor are accommodated in the oil tank together with the insulating oil.

  The lead conductor requires a relatively large volume in order to dissipate heat when energized. Further, the lead conductor is driven at a high speed together with the movable shaft having the movable electrode, particularly during the closing operation, in order to ensure the energization performance at the time of tap switching.

JP-A-3-235308 JP-A-3-83310 JP 2002-50267 A

  By the way, when the vacuum valve is closed, negative pressure is generated as the insulating oil between the vacuum valve and the lead conductor flows out rapidly due to the movement of the lead conductor together with the movable shaft at high speed. There is. At this time, the gas dissolved in the insulating oil becomes saturated and causes aeration, which appears as bubbles.

  In addition, if the insulation oil flows between the vacuum valve and the lead conductor due to the sudden stop of the operation after the closing operation is completed and the pressure is restored, the bubbles generated in the insulation oil collapse and the energy at the time of the collapse is lost. Will cause a big impact. If bubbles are repeatedly generated and collapsed by aeration each time the vacuum valve is closed, the surface of the extraction conductor facing the vacuum valve and the peripheral surface of the movable shaft between the vacuum valve and the extraction conductor are damaged. In some cases, erosion may occur, and when the erosion progresses, the movable shaft may be broken starting from the erosion mark.

  Therefore, the problem to be solved by the present invention is to provide an on-load tap switching device capable of suppressing the occurrence of aeration.

The on-load tap switching device of the embodiment includes a vacuum valve, a lead conductor, an oil tank, and a negative pressure reduction mechanism. The vacuum valve includes a movable shaft having a movable electrode paired with a fixed electrode at one end and the other end protruding outward. The lead conductor is a relay terminal portion fixed to the other end portion of the movable shaft so as to face the vacuum valve. The oil tank accommodates the vacuum valve and the lead conductor together with the insulating oil. The negative pressure reducing mechanism reduces the generation of negative pressure due to the flow of insulating oil when the extraction conductor approaches the vacuum valve by the closing operation of the vacuum valve. The negative pressure reducing mechanism includes a through hole for oil draining formed so as to penetrate the lead conductor along the axial direction of the movable shaft.

The front view which shows the tap switching apparatus at the time of load which concerns on 1st Embodiment. The perspective view which shows the structure of the switching switch with which the tap switching apparatus at the time of a load of FIG. The front view which shows the structure of the periphery of the vacuum valve with which the switching switch of FIG. The figure for demonstrating the erosion phenomenon which may arise between the vacuum valve of FIG. 3, and an extraction conductor. The perspective view which shows the structure of the extraction conductor of FIG. 3 provided with a negative pressure reduction mechanism. The perspective view which shows the structure of the extraction conductor of a comparative example. The figure which shows the result of the fluid analysis when the extraction conductor of FIG. 5 is applied. The figure which shows the result of the fluid analysis when the extraction conductor of the comparative example of FIG. 6 is applied. The perspective view which shows the structure of the extraction conductor provided with the other negative pressure reduction mechanism in which a partial structure differs from the negative pressure reduction mechanism of FIG. The figure which shows the result of the fluid analysis when the extraction conductor of FIG. 9 is applied. The figure which shows the form which has arrange | positioned the protection member between the vacuum valve and drawing conductor of FIG. FIG. 4 is a perspective view schematically showing a form in which a speed limiting mechanism for limiting the operation speed of the lead conductor in FIG. 3 is provided around the vacuum valve. The figure which shows a form when a damper is applied as a speed limiting mechanism of FIG. The figure which shows a form when a spring is applied as a speed limiting mechanism of FIG.

Hereinafter, embodiments will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the on-load tap changer 10 according to the present embodiment is a vacuum interrupter type on-load tap changer (VI-LTC). Built into the transformer connected to the power transmission and distribution system.

  As shown in FIG. 1, the on-load tap switching device 10 mainly includes a switching switch 12, a tap selector 11, and an oil tank 15. The oil tank 15 is installed in a tank that becomes a casing of the transformer. The oil tank 15 is filled with insulating oil. The switching switch 12 is accommodated in the oil tank 15 together with the insulating oil.

  The tap selector 11 includes a movable contact between the tap winding and the neutral point, and the tap of the tap winding is selected by the movable contact. On the other hand, as shown in FIG. 1, the change-over switch 12 includes a change-over switch, creates a short circuit state via a resistor between a pair of taps selected by the tap selector 11, and loads by the change-over switch. Switch taps to pass current. That is, the switching switch 12 can switch the voltage without interrupting the load current.

  Specifically, as shown in FIG. 2, the switching switch 12 suppresses the circulating current of the energizing unit when the tap is switched, and the accumulating mechanism 16 that accumulates the power for switching the tap (accumulates elastic energy). A current limiting resistor 17, a three-phase energization switching mechanism 14 for changing the energization path, and a drive shaft 19. The energization switching mechanism 14 includes a vacuum valve (VCB: vacuum circuit breaker) 18 and the above-described changeover switch.

  Here, the energization switching mechanism 14 of the switching switch 12 has two current limiting resistors 17 and three vacuums for each phase (each of the three phases) as a switching method when changing the energization path. A 2 resistance 3 vacuum valve system using the valve 18 is applied. In the 2-resistance 3-vacuum valve system, the current limiting resistor 17 suppresses the circulating current that flows at the time of switching, and the vacuum valve 18 performs a circuit breaking operation.

  That is, the vacuum valve 18 is a set of a main vacuum valve and two resistance vacuum valves. The changeover switch includes two fixed contacts and a movable contact. The main vacuum valve is connected in series with the changeover switch. The resistance vacuum valve is connected in parallel to the main vacuum valve and in series with the current limiting resistor 17.

  Briefly describing the opening and closing operations of these three vacuum valves, the main vacuum valve is in a closed state, the resistance vacuum valve on the energizing tap side is in the closed state, and the non-energizing tap side is in the state before the changeover operation of the changeover switch. Assume that the resistance vacuum valve is in an open state. From this state, when the changeover switch starts the changeover operation, the resistance vacuum valve on the non-energizing tap side is closed during the changeover operation. Next, when the main vacuum valve is opened and the changeover operation of the changeover switch is finished, the main vacuum valve is closed. Finally, the resistive vacuum valve that was energized before the switching operation is opened.

  In the energization switching mechanism 14, when the drive shaft 19 is rotated by the elastic energy released from the accumulator mechanism 16, this rotational force is transmitted to the cam 21 as shown in FIGS. 18 is opened and closed. The above-described changeover switch performs a changeover operation in conjunction with the rotation of the cam 21.

  Next, the structure around the vacuum valve 18 and the internal structure of the vacuum valve 18 will be described with reference to FIG. FIG. 3 is a cross-sectional view of the left side from the central axis of the vacuum valve 18. As shown in FIG. 3, a copper lead conductor 22, a connecting rod 23, a compression spring 24, a drive boss 25, a cam floor 36, and the cam 21 are provided around the vacuum valve 18. The vacuum valve 18 includes a fixed electrode 27, a movable shaft 28, an insulator 29, and a bellows (flexible tube) 30 inside.

  The movable shaft 28 has a movable electrode 31 paired with the fixed electrode 27 at one end portion 28 a, and the other end portion 28 b protrudes from the inside of the main body of the vacuum valve 18. The vacuum valve 18 has a sealing structure with an insulator 29, a lower flange 33, an upper flange 34, and a bellows 30 so that a contact portion 32 between the movable electrode 31 and the fixed electrode 27 at one end portion 28a of the movable shaft 28 is evacuated. Configure.

  A flat braided wire (flexible cable) is connected to the lead conductor 22. The lead conductor 22 is a relay terminal portion (relay terminal conductor) connected to another energization portion via the flat knitted wire. As shown in FIG. 3, the lead conductor 22 is fixed to the other end 28 b of the movable shaft 28 so as to face the vacuum valve 18. Specifically, a male screw is formed on the peripheral surface of the other end 28 b of the movable shaft 28. On the other hand, a screw hole (female screw) 22 a for fixing the movable shaft is formed in the central portion of the lead conductor 22. Accordingly, the lead conductor 22 is fastened (fixed) to the other end portion 28b of the movable shaft 28 through the screw hole 22a.

  A male thread is formed on the peripheral surface of the one end 23 a of the connecting rod 23. A screw hole is formed in the other end 28 b of the movable shaft 28. As a result, the one end 23 a of the connecting rod 23 and the other end 28 b of the movable shaft 28 are fastened to each other within the screw hole 22 a of the lead conductor 22. Here, the connecting rod 23 is disposed so as to pass through both a predetermined rod insertion hole provided in the drive boss 25 having an L-shaped cross section and the inner diameter portion of the compression spring 24.

  Specifically, as shown in FIG. 3, the compression spring 24 is sandwiched between the rod head 23 b provided at the other end of the connecting rod 23 and the lead conductor 22 via the drive boss 25. The connecting rod 23 is fastened to the movable shaft 28. Thereby, the movable electrode 31 at the one end portion 28 a of the movable shaft 28 fixed to the lead conductor 22 is urged toward the fixed electrode 27 (in the direction of the arrow Y <b> 2) by the elastic force of the compression spring 24.

  Further, as shown in FIG. 3, a cam floor 36 that is engaged with the cam groove 21 a of the cam 21 described above is fixed to the side surface of the drive boss 25. Therefore, as shown in FIGS. 2 and 3, the cam 21 interlocking with the rotation of the drive shaft 19 of the energization switching mechanism 14 operates to raise the cam floor 36 in the direction of the arrow Y1 when the vacuum valve 18 is opened. Accordingly, the drive boss 25, the connecting rod 23, the lead conductor 22, and the movable shaft 28 rise together, and the movable electrode 31 at the one end portion 28 a of the movable shaft 28 is separated from the fixed electrode 27 side. To work.

  On the other hand, during the closing operation of the vacuum valve 18, the cam 21 operates to lower the cam floor 36 in the direction of arrow Y 2, and accordingly, the drive boss 25, the connecting rod 23, the lead conductor 22, and the movable shaft 28 are moved. The movable electrode 31 descends as a unit and is located at one end portion 28a of the movable shaft 28 so as to come into contact with the fixed electrode 27 side.

  Here, the erosion phenomenon that may occur between the vacuum valve 18 and the lead conductor 22 during the closing operation of the vacuum valve 18 will be described mainly with reference to FIGS. 4 (a) to 4 (f). As described above, the switching switch 12 including the vacuum valve 18 and the lead conductor 22 is accommodated in the oil tank 15 together with the insulating oil. For this reason, the periphery of the vacuum valve 18 and the lead conductor 22 is filled with insulating oil except for the contact portion 32 in a vacuum state shown in FIG.

First, as shown in FIG. 4 (a), at the start of the closing operation of the vacuum valve 18, the lead conductor 22 through the movable shaft 28 is close to the vacuum valve 18 side while greatly accelerate the operating speed S ₁ . At this time, the insulating oil is compressed by the lead conductor 22, so that a relatively small fluid (insulating oil) n flows. That is, small fluid velocity S ₂ of the insulating oil, the facing surfaces 22e of the vacuum valve 18 in the lead conductor 22, the positive pressure acts fluid pressure in the opposite direction resulting from the operation direction of the lead conductor 22.

As shown in FIG. 4B, as the closing operation proceeds, the operation speed S ₁ of the lead conductor 22 is reduced, but the fluid speed S ₂ of the insulating oil is maintained by the inertial force. Therefore, the relative speed relationship between the operating speed S ₁ of the lead conductor 22 and the fluid speed S ₂ of the insulating oil is reversed, and the flow direction of the fluid n is between the lead conductor 22 and the vacuum valve 18. The fluid pressure along the line acts and a negative pressure is generated.

As shown in FIG. 4C, when the closing operation is completed, the relative fluid velocity S ₂ with respect to the operation velocity S ₁ of the lead conductor 22 becomes maximum, and at this time, between the lead conductor 22 and the vacuum valve 18. The maximum negative pressure is generated. In this case, when the pressure drops below the saturated vapor pressure, as shown in FIG. 4D, aeration is generated in which the air dissolved in the insulating oil is vaporized and appears as bubbles p.

  After the closing operation is completed, when the insulating oil returns between the lead conductor 22 and the vacuum valve 18 and the pressure returns to a positive pressure, a compressive force is applied to the bubble p, as shown in FIG. The bubble p will collapse. In this case, as shown in FIG. 4 (f), erosion occurs on the opposing surface 22e of the lead conductor 22 and the peripheral surface 28c of the movable shaft 28 between the lead conductor 22 and the vacuum valve 18 due to the collapse energy of the bubbles. A mark k may occur.

  Therefore, in the on-load tap switching device 10 of the present embodiment, as shown in FIG. 5, the lead conductor 22 is provided with a negative pressure reducing mechanism 35. The negative pressure reduction mechanism 35 reduces the generation of negative pressure due to the flow of insulating oil when the extraction conductor 22 approaches the vacuum valve 18 by the closing operation of the vacuum valve 18.

  Specifically, as shown in FIG. 5, a screw hole 22a for fixing the movable shaft in the center of the rectangular lead conductor 22 and a pair of flat knitting wire mounting holes drilled at positions sandwiching the screw hole 22a from both sides. A pair of through holes 22c and 22d for draining oil is formed in the lead conductor 22 as a negative pressure reducing mechanism 35 between the lead holes 22b. The oil draining through holes 22 c and 22 d are perforated so as to penetrate the lead conductor 22 along the axial direction of the movable shaft 28.

  The through holes 22c and 22d for draining oil allow the insulating oil to pass smoothly without being compressed when the extraction conductor 22 approaches the vacuum valve 18 when the vacuum valve 18 is closed. The generation of a negative pressure between 22 and the vacuum valve 18 can be suppressed. Thereby, since generation | occurrence | production of the aeration (bubble) in insulating oil can be suppressed, it can avoid that the opposing surface 22e of the extraction conductor 22 and the surrounding surface 28c of the movable shaft 28 are eroded. Become.

  Here, FIG. 7 is a fluid analysis showing the pressure distribution of the insulating oil when the extraction conductor 22 of FIG. 5 having through holes 22c and 22d for oil draining is applied and the vacuum valve 18 is closed. Results are shown. On the other hand, FIG. 8 shows a fluid analysis representing the pressure distribution of insulating oil when the vacuum valve 18 is closed by applying the lead conductor 62 of the comparative example shown in FIG. 6 without a through hole for draining oil. Results are shown.

  7 and 8, an arrangement portion 22f of the screw hole 22a for fixing the movable shaft is shown in the center region, and the darker the color, the greater the negative pressure value. That is, from the results of the fluid analysis shown in FIGS. 7 and 8, in the lead conductor 22 having the through holes 22c and 22d for draining oil, the generation of negative pressure is reduced compared to the lead conductor 62 of the comparative example. (The negative pressure value is about 11% smaller), which makes it possible to suppress the occurrence of aeration.

  FIG. 9 shows a lead conductor 42 provided with a negative pressure reducing mechanism 35. The negative pressure reducing mechanism 45 of the lead conductor 42 is a tapered portion provided around the movable shaft 28 on the surface 22e of the lead conductor 42 facing the vacuum valve 18 in addition to the above-described through holes 22c and 22d for draining oil. 46 is further included. The tapered portion 46 is inclined so that an outer edge portion (portion where the maximum negative pressure is generated) of the movable shaft 28 is raised toward the vacuum valve 18 side. The tapered portion 46 suppresses the generation of negative pressure by radially dispersing the fluid (insulating oil) in contact with the tapered portion 46 during the closing operation of the vacuum valve 18 from the outer edge side of the movable shaft 28.

  The angle of the taper portion 46 (inclination angle between the opposing surface 22e and the flat surface) is, for example, 30 °, and is desirably within a range of at least 20 ° and 45 °. If the angle of the tapered portion 46 is less than 20 ° or exceeds 45 °, it is difficult to properly disperse the fluid (insulating oil) that contacts the tapered portion 46 during the closing operation of the vacuum valve 18.

  FIG. 10 shows the result of fluid analysis representing the pressure distribution of insulating oil when the lead conductor 42 of FIG. 9 having the negative pressure reducing mechanism 45 is applied and the vacuum valve 18 is closed. As can be seen from the results of the fluid analysis, in the lead conductor 42 shown in FIG. 9, the generation of negative pressure is reduced compared to the lead conductor 62 in the comparative example shown in FIG. 6 (the value of the negative pressure is about 21). The risk of erosion is reduced.

  Further, FIG. 11 illustrates a form in which an O-ring 47 is further arranged as a protective member having elasticity in addition to providing the above-described negative pressure reducing mechanism. The O-ring 47 protects the peripheral surface (male thread portion) 28 c between the vacuum valve 18 and the lead conductor 22 in the movable shaft 28.

  Since the O-ring 47 can guard the peripheral surface of the movable shaft 28 from the impact generated when the bubble collapses even if bubbles are generated and collapsed during the closing operation of the vacuum valve 18, the movable shaft 28 is damaged. Can be prevented.

  FIG. 12 illustrates a negative pressure reducing mechanism 55 that includes a speed limiting mechanism 56. The speed limiting mechanism 56 limits (decelerates) the operating speed of the lead conductor 22 when the lead conductor 22 approaches the vacuum valve 18 by the closing operation of the vacuum valve 18. The speed limiting mechanism 56 includes a brake pad 57.

  The brake pad 57 is fixed to the drive boss 25. When the vacuum valve 18 is closed, the brake pad 57 is slid with, for example, the inner wall portion of the casing of the switching switch 12, so that the drive boss 25 and the movable shaft are moved. The operating speed of the lead conductor 22 that operates together with 28 and the like is limited. As a result, it is possible to avoid abrupt compression and flow of the insulating oil between the vacuum valve 18 and the lead conductor 22, and to suppress the occurrence of aeration due to the generation of negative pressure.

  FIG. 13 shows a negative pressure reducing mechanism 75 including a speed limiting mechanism 76. The speed limiting mechanism 76 has a damper 77 made of an elastic body such as rubber. The damper 77 is pushed by the drive boss 25 and elastically deformed during the closing operation of the vacuum valve 18, thereby limiting the operation speed of the lead conductor 22 that operates integrally with the drive boss 25.

  FIG. 14 illustrates a negative pressure reducing mechanism 85 including a speed limiting mechanism 86. The speed limiting mechanism 86 has a compression spring 87 interposed between the vacuum valve 18 and the lead conductor 22. The compression spring 87 limits the operating speed of the lead conductor 22 by being pushed and elastically deformed by the lead conductor 22 when the vacuum valve 18 is closed.

  Since the generation of aeration can also be suppressed by the negative pressure reducing mechanisms 75 and 85 including the speed limiting mechanisms 76 and 86 shown in FIGS. 13 and 14, it is possible to prevent erosion of the lead conductor 22 and the movable shaft 28. It becomes. Further, by applying the damper 77 and the compression spring 87 shown in FIGS. 13 and 14, the closing operation can be decelerated, while the opening operation can be accelerated by the elastic force of the damper 77 and the compression spring 87. Therefore, the closing operation and the opening operation suitable for the tap switching operation can be realized.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Tap switching device at the time of loading, 15 ... Oil tank, 18 ... Vacuum valve, 22, 42 ... Lead-out conductor ... Lead-out conductor, 22c, 22d ... Through hole for oil draining, 22e ... Opposite surface, 27 ... Fixed electrode, 28 ... Movable shaft, 28a ... one end of the movable shaft, 28b ... other end of the movable shaft, 28c ... peripheral surface of the movable shaft, 31 ... movable electrode, 35, 45, 55, 75,85 ... negative pressure reducing mechanism, 46 ... Tapered portion, 47 ... O-ring, 56, 76, 86 ... speed limiting mechanism, 57 ... brake pad, 77 ... damper, 87 ... compression spring.

Claims (8)

A vacuum valve provided with a movable shaft having a fixed electrode and a pair of movable electrodes at one end and the other end protruding to the outside;
A lead conductor serving as a relay terminal fixed to the other end of the movable shaft so as to face the vacuum valve;
An oil tank for housing the vacuum valve and the lead conductor together with insulating oil;
A negative pressure reduction mechanism that reduces the generation of negative pressure accompanying the flow of the insulating oil when the lead conductor approaches the vacuum valve by the closing operation of the vacuum valve;
Bei to give a,
The negative pressure reduction mechanism, along the axial direction of the movable shaft includes a through hole for the formed oil drain which to penetrate the lead conductor, the load tap changer unit. A vacuum valve provided with a movable shaft having a fixed electrode and a pair of movable electrodes at one end and the other end protruding to the outside;
A lead conductor serving as a relay terminal fixed to the other end of the movable shaft so as to face the vacuum valve;
An oil tank for housing the vacuum valve and the lead conductor together with insulating oil;
A negative pressure reduction mechanism that reduces the generation of negative pressure accompanying the flow of the insulating oil when the lead conductor approaches the vacuum valve by the closing operation of the vacuum valve;
With
The negative pressure reduction mechanism, said lead conductor the said movable shaft including a tapered portion provided around the on the surface facing the vacuum valve, the load tap changer unit. A vacuum valve provided with a movable shaft having a fixed electrode and a pair of movable electrodes at one end and the other end protruding to the outside;
A lead conductor serving as a relay terminal fixed to the other end of the movable shaft so as to face the vacuum valve;
An oil tank for housing the vacuum valve and the lead conductor together with insulating oil;
A negative pressure reduction mechanism that reduces the generation of negative pressure accompanying the flow of the insulating oil when the lead conductor approaches the vacuum valve by the closing operation of the vacuum valve;
A protective member for protecting a peripheral surface between said vacuum valve before Symbol movable shaft the lead conductors,
Load tap changer apparatus comprising a. The on-load tap switching device according to claim 3 , wherein the protection member has elasticity. The on-load tap switching device according to claim 4 , wherein the protective member is an O-ring. The negative pressure reduction mechanism includes a speed limiting mechanism that limits an operation speed of the lead conductor when the lead conductor approaches the vacuum valve by a closing operation of the vacuum valve.
The on-load tap switching device according to any one of claims 1 to 5 . The on-load tap switching device according to claim 6 , wherein the speed limiting mechanism includes a damper. The on-load tap switching device according to claim 6 , wherein the speed limiting mechanism includes a spring.

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